Ultrasonication of Milky Stage Rice Milk with Bioactive Peptides from Rice Bran: Its Bioactivities and Absorption

Rice in early development stage contains peptides and various bioactive compounds. Rice protein hydrolysate was prepared from Riceberry bran protein hydrolysed with Alcalase® and trypsin. Protein hydrolysate from Alcalase® (MW < 3 kDa) was fractionated into 12 fractions using RP-HPLC and tested for antioxidant, ACE, and ROS-inhibitory activity. Peptide from RP-HPLC fraction 1 showed that the lowest ROS inhibition and highest antioxidant were identified by LC-MS/MS as Val-Leu-Ala-Ala-Gly-Cys-Pro-Leu. Peptide fraction 4 showed that the strongest in vitro ACE-inhibitory activity was identified as Ala-Met-Ser-Phe-Ala-Glu-Met. Young Riceberry milk was then enriched with Alcalase® protein hydrolysate (MW < 3 kDa) and sonicated at amplitude 20% for 30 min and 40% for 60 min. Particle size, transmittance, and Caco-2 cell absorption were measured. The highest peptide content and % absorption was found in young rice milk ultrasonicated at 40% for 60 min. Rice bran protein hydrolysate produced by Alcalase® had much smaller MW bioactive peptides and could be used as a potent functional food ingredient. The young rice milk fortified with bioactive peptides after high power ultra-sonication could increase the in vitro intestinal absorption.